Electronic Enclosures

Chapter 1: What is the principle of electronic enclosures?

This chapter will cover the concept of electronic enclosures and the processes involved in their manufacturing.

What is an Electronic Enclosure?

Electronic enclosures are box-like structures designed to protect and house electronic components such as switches, relays, printed circuit boards (PCBs), integrated circuits, power supplies, and processors. These enclosures come in various materials and sizes, tailored to their specific use, purpose, environment, and cost considerations. The diagram below illustrates an electronic enclosure safeguarding its internal components.

Consider an electronic device that is vulnerable to water ingress, easily accessible to children, or exposed to heat and moisture. Such a device would likely suffer from damage due to environmental factors and pose hazards to users. To address these issues, electronic and electrical engineers have developed protective structures to shield devices from environmental damage and other risks associated with exposed components. These protective structures are known as electronic enclosures.

What is a Metal Box?

A metal box is a designed fabrication to give shelter, store, and enclose something. Aluminum enclosures and stainless steel enclosures are all referred to as the types of metal boxes. Metal boxes are commonly used as fuse boxes and outdoor electrical meters. In business companies, these metal boxes are often used for enclosing electrical equipment for the supply of power around the premises.

In industrial settings, electronic enclosures protect sensitive and delicate components from accidental impacts, debris, dirt, and contamination. These enclosures help prevent damage from accidents involving workers or machinery, reducing the risk of severe issues such as explosions or electrical faults.

The International Electrotechnical Commission (IEC) provides guidance for selecting appropriate enclosures and ratings based on their intended use. For example, metal enclosures used in telecommunications must be carefully chosen to avoid obstructing or interfering with information flow. Selecting the wrong type of enclosure can lead to significant operational problems.

How are Electronic Enclosures Made

Several methods are commonly used to fabricate electronic enclosures, including the ones outlined below.

CNC Machining

Computer Numerically Controlled (CNC) machining utilizes subtractive processes where a machine reads CAD files to guide a cutting tool. This allows the tool to precisely cut the material according to the specifications provided in the CAD program.

The process on CNC machines is repeatable if the program files are still accessible to the machine. This is an advantage because the same program used to manufacture a plastic enclosure can be used to fabricate a metal enclosure. CNC machining enables the fabrication of complex geometric designs.

Sheet Metal Fabrication

Sheet metal fabrication involves transforming flat metal sheets, typically made of aluminum or steel, into metallic structures through processes such as folding and assembling. This method is both efficient and cost-effective for producing electronic enclosures. Compared to CNC machining, sheet metal fabrication is generally faster and less complex.

Sheet metal fabrication is commonly used for manufacturing outdoor and desktop electronic enclosures. While the initial investment in sheet metal fabrication equipment and tools can be high, the cost per part decreases significantly as production volume increases.

Injection Molding

Injection molding is a manufacturing process that involves shaping materials such as plastic, metals, glasses, elastomers, polymers, and injecting heated material into the mold. This method is mainly used when manufacturing simple enclosures like car remote controls, tv remote controllers, gamepads, kiosk displays, calculators, etc.

3D Printing

3D printing is an additive manufacturing technique that creates enclosures by building up layers of material based on CAD files. This process allows for the production of complex designs that might be challenging or impossible to achieve with methods like injection molding.

Both plastic and metal materials can be used in 3D printing; however, most 3D printers are slower compared to traditional production methods. 3D printing is ideal for small production runs, custom enclosures with unique designs, or for prototyping models before scaling up to mass production.

Factors to Consider When Designing Electronic Enclosures

When designing electronic enclosures, several key factors should be taken into account, including:

Product Requirements

Product requirements encompass the features, functions, and operational characteristics that an electronic product must have. This information is typically detailed in a document known as the Product Requirements Document (PRD), which provides guidelines on how the product should function.

The PRD aids in creating an electronic enclosure that meets these specific requirements. For instance, the PRD may specify functions such as heat dissipation, moisture protection, vibration absorption, visibility of LEDs, and accommodation for a fan. By referring to the PRD, designers can determine the appropriate materials, costs, and manufacturing processes needed for the enclosure.

Modeling the Internal Components

Designing an optimal enclosure requires a thorough understanding of how the internal components will be arranged. This involves knowledge of circuit design and electronic layout. For example, holes should be drilled where necessary, and spaces should be allocated for heat dissipation or ventilation if heat-absorbing components are used.

Some components cannot be placed adjacent to one another due to issues such as interference, false readings, short circuits, or overheating, which can shorten their lifespan. Considering these factors is crucial for effective design. For the best results, it is advisable to consult with or hire professionals who have expertise in these areas.

Creating the Shell of the Enclosure

Once the electronic components are modeled, the enclosure shell can be designed by taking into account the arrangement of the parts. Before selecting a manufacturing process, it is crucial to create a 3D CAD model of the enclosure. This allows for adjustments and corrections if any misalignments are found.

Wall thickness is a critical consideration in the design of the enclosure. If the walls are too thin, the enclosure may be vulnerable to damage under harsh conditions. Conversely, if the walls are too thick, they might trap heat, which could pose a risk to the device's overall functionality.

Comparing the CAD with the BOM

Before proceeding with the production of the actual enclosure, it is crucial to compare the CAD model with the Bill of Materials (BOM) to prevent any communication issues. This comparison is most efficiently performed using specialized software tools.

Chapter 2: What are the types of electronic enclosures?

Electronic enclosures can be categorized based on the material used and their specific applications.

Classification According to Material Type

Electronic enclosures are typically made from either metals or plastics, resulting in two common types: metal enclosures and plastic enclosures.

Metal Enclosures

Metal enclosures are commonly used in buildings for various applications, such as fuse boxes and meter boxes. These enclosures are designed to protect internal components from accidental impacts, contamination from dust and dirt, and other hazardous conditions. They are typically chosen for applications where portability is not a major concern.

In industrial settings, metal enclosures offer robust protection for equipment, creating a safe and effective working environment. Given the high levels of dirt and debris in industrial environments, metal enclosures are particularly suitable because of their strength and durability, making them ideal for withstanding harsh conditions.

Metal enclosures are available in a wide range of sizes, tailored to their specific applications. For instance, in substations where electrical and power distribution occurs, large enclosures are commonly used. Conversely, smaller metal enclosures are found in consumer devices like light switch fixtures. These enclosures can come in various shapes, including box, cylindrical, and rectangular cylindrical forms, depending on their intended use and the manufacturer's capabilities for metal punching and fabrication.

Aluminum Enclosures

Aluminum enclosures are designed to safeguard electronic components from various types of damage, including electromagnetic interference. These enclosures are suitable for both indoor and outdoor use, protecting devices from adverse weather conditions such as excessive heat, moisture, UV radiation, as well as from dust and dirt contamination.

Exposure to such conditions can lead to electromagnetic interference and other circuit disruptions. Consequently, many electronic devices, including computers, are housed in unibody aluminum enclosures to ensure durability and protection. Aluminum enclosures are also commonly used in handheld devices like remotes, power switches, electrical conduits, garage door openers, and car starters.

Design of Aluminum Enclosures

Designing aluminum electronic enclosures involves comprehending:

• Material Type: Aluminum enclosures are made from aluminum, although other materials can be used for enclosures. Aluminum has different alloys, which are applied differently to these enclosures depending on the use and type of environment the device is exposed to.
• Size and Shape: Most of the aluminum enclosures have a box-like shape with corresponding dimensions but in general, they have lengths ranging from 10 cm to 20 cm. Other different dimensions can be used depending on the specific design of the enclosure.
• Door Type: These types of enclosures usually have a hinged solid lid door. A hinged door can be used where security is needed the most to lock the enclosure. In other enclosures, there are internal gaskets used as well continuous flanges for complete closure of the box and this protects the device from dirt, dust, and moisture. Sometimes the doors are made from the bezel and corner screws, especially when a tight closure is required. These methods of closing aluminum enclosures can be combined for an effective enclosure if need be.

Stainless Steel Enclosures

Stainless steel, composed of iron combined with chromium and occasionally nickel, is known for its corrosion resistance. Often regarded as an eco-friendly material due to its recyclability, stainless steel enclosures are used to safeguard electronic components in both indoor and outdoor settings. While their designs and manufacturing processes are similar to other materials, differences in properties such as density, resistance to corrosion, and cost set them apart.

Plastic Enclosures

Plastic enclosures are containers designed to shield and house electronic components. Typically molded into various shapes to meet product specifications, plastic materials offer flexibility and are lightweight, making them ideal for creating portable devices.

In cases where insulation is required, plastic enclosures are usually the best to use. Common examples of plastic enclosures are found in calculators, remote controls, desktop computers, laptop computers, wireless internet controllers, coolers, game controllers, and televisions.

Design of Plastic Enclosures

When designing plastic enclosures, several factors need to be considered:

Plastic Material Type

A variety of plastic materials can be used for electronic enclosures, with some being used alone while others may be combined. The choice of plastic depends on the specific requirements of the application. For more demanding uses, high-density polyethylene (HDPE) is often selected due to its robustness as a thermoplastic material.

HDPE is valued for its resistance to cold, liquids, and corrosion, its durability, resistance to high temperatures, and its cost-effectiveness in production. Other plastics used include acrylic, polyvinyl chloride (PVC), polypropylene, acrylonitrile butadiene styrene (ABS), styrene ethylene butadiene styrene (SEBS), and polyamide (PA).

Here are some commonly used materials for manufacturing plastic electronic enclosures:

• Acrylonitrile Butadiene Styrene (ABS): Acrylonitrile Butadiene Styrene is used to manufacture plastic enclosures and is very effective, especially when used in environments where resistivity to chemicals is required and shielding from impacts. ABS has poor resistivity to ultraviolet (UV) light and is effective for indoor enclosures.
• Acrylonitrile Styrene Acryl Ester (ASA): Acrylonitrile Styrene Acryl Ester is used in applications such as food manufacturing, healthcare, pharmaceutical or laboratory facility, wellness because of its antimicrobial properties. In environments where there are fungi and viruses, ASA is well protected and can be mounted in bacteria-prone areas.
• Combination of Polycarbonate and Acrylonitrile Styrene Acryl Ester: Sometimes the best electronic enclosures are brought about by combining the different properties in materials to bring the best enclosure. When Polycarbonate is combined with Acrylonitrile Styrene Acryl Ester, this enables the enclosure to have flame resistance, withstand high temperatures, ensure resistance to weather and chemicals, survive in impact-ridden environments, and make the product usable for outdoor environments. Many properties can be attained but combining materials and such enclosures is usually expensive and durable.
• Carbon Neutral Bioplastic: Carbon Neutral Bioplastic is a new type of plastic that is biodegradable. These types of materials are used where there is a need for soft case enclosures. They are naturally occurring, and they are certified biodegradable.

Enclosure Classification According to Application

Enclosures can also be classified according to their application. Some of them are:

Computer Enclosures

Computer enclosures are designed to safeguard computer hardware from potential damage and contamination caused by dirt, moisture, and dust. These protective cases are crucial in ensuring the longevity and functionality of computer components. Today, computer enclosures are prevalent in a wide range of environments including homes, offices, spacecraft, vehicles, factories, and even portable devices like bags and pockets.

Computer enclosures are designed based on the environment in which the computer is going to operate, for example a home computer is exposed to dust, exposure to liquids, and impacts from the accident. A computer used for industrial purposes is exposed to the same impacts but to a greater extent. In heavy manufacturing industries computer enclosures are supposed to be designed to protect the computer from flying debris, unwanted temperature ranges, and protection from moving machinery and workers.

Design of Computer Enclosures

When designing a computer case, the following factors should be taken into account:

Computer Enclosure Intended Use

Enclosures for computers used in vehicles need to be engineered to protect against vibrations and impacts caused by driving and engine operations.

Computer enclosures, including those for laptops, should be constructed from lightweight materials for easy portability while still being durable enough to withstand accidental impacts.

Computer Material Type

Computer enclosures are crafted from various materials based on factors such as application, cost, and durability. Common metals used include aluminum and stainless steel, particularly when portability and weight are less of a concern. In contrast, many laptops feature enclosures made from lighter metals or plastics like ABS (acrylonitrile butadiene styrene) to enhance portability.

The National Electronics Manufacturers Association (NEMA) aids electronic manufacturers by offering ratings that help determine the suitability of enclosure materials for different applications. These ratings indicate whether an enclosure is appropriate for indoor or outdoor use. For instance, ratings such as 1, 2, 12, 12K, and 13 are designed for indoor environments with minimal contamination risk. NEMA provides guidance on enclosures for both low and high hazard conditions, whether indoor or outdoor.

Custom Enclosures

Custom enclosures are developed when standard electronic enclosures do not meet specific or unique requirements. These enclosures are created from the ground up, beginning with a design concept tailored to fit the exact needs of the application.

Essentially, a custom electronics enclosure is a carefully crafted solution that matches the precise dimensions and components required for the space. Often made from plastic to meet specific needs like UV protection for indoor use, these enclosures are sometimes based on standard models that are modified to address unique conditions.

While most electronic enclosures have a box-like shape, some applications require irregular or custom shapes. This might involve designing for curves, contours, or other complex geometries. Materials like aluminum, galvanized steel, and stainless steel are frequently chosen for their strength and durability, whereas plastics are typically used for more intricate and small-scale designs.

Portable Enclosures

Portable enclosures are designed to be compact enough to fit in a pocket or be easily held in hand. They are commonly used for devices such as LEDs and battery compartments. Examples of portable enclosures include car key fobs, laptop cases, computer mice, and TV remote controls.

Desktop Enclosures

Desktop enclosures are built to safeguard computers in office or industrial settings from dust and other contaminants. Components such as the Central Processing Unit (CPU) are sensitive, so these enclosures often include features like engravings, footpads, and removable stands to facilitate easy relocation if necessary.

Display Enclosures

Display enclosures, such as those with touch screens and transparent windows, are widely used today. These enclosures shield screens from sunlight, impacts, and liquid spills. They are typically constructed from glass and plastic, as these materials are well-suited for maintaining visibility while protecting colorless displays.

Wall-Mounted Enclosures

Wall-mounted enclosures, as the name suggests, are designed to be fixed to walls while safeguarding electronic equipment from damage, contaminants, heat, and other hazardous conditions. These enclosures are commonly made from a combination of plastic and metal materials.

Cabinet Enclosures

Cabinet enclosures are primarily used to protect equipment related to video and audio production, including cameras and televisions.

NEMA (National Electrical Manufacturers Association) Enclosures

NEMA enclosures are common in many industries such as telecommunication, rain services, bus services, electronics, domestic and commercial appliances, security, aviation, sound and music, defense and rail services. They are seen in nuclear power plants housing the wiring in nuclear reactors and control rooms. NEMA is a group that intends to bring manufacturers together so that they come under the umbrella of expanding markets and increase their profits by reducing manufacturing costs of products.

Materials Used for NEMA Enclosures

NEMA enclosures are commonly constructed from materials like polycarbonate and various steel and aluminum alloys, including 316 stainless steel, 304 stainless steel, and 5022 aluminum powder-coated carbon steel. Polycarbonate, a high-temperature resistant thermoplastic, boasts impact resistance approximately five times greater than fiberglass. It is also resistant to heat, water, impact, and flames, and offers excellent insulation properties. Enclosures made from polycarbonate are suitable for low-temperature environments. NEMA enclosures can be designed in various forms such as junction boxes, free-standing units, troughs, floor mounts, wall mounts, and free-standing designs with leg kits.

EMI Enclosures

EMI, or electromagnetic interference, is also referred to as Radio Frequency Interference (RFI) in electronics. This type of disturbance arises from external sources and can interfere with electrical and electronic circuits and components. EMI enclosures are engineered to shield electronic devices from unwanted interferences caused by electromagnetic fields, radiation, coupling effects, and other potential disruptions. Common sources of electromagnetic interference include toaster ovens, automobile ignition systems, thunderstorms, electric blankets, the sun, and computer monitors. These enclosures prevent interference by blocking, conducting, absorbing, or reflecting electromagnetic energy.

Materials Used for EMI Enclosures

EMI enclosures are typically constructed from various metals, including solid and perforated types. An example is a microwave door, which prevents microwaves from escaping the appliance. Metals such as aluminum, copper, nickel, steel, stainless steel, and their alloys are frequently used to build EMI enclosures. Sometimes, manufacturers apply metal coatings to plastic materials, which still qualifies as an EMI enclosure. These enclosures are used across multiple industries including food and beverage services, telecommunications, stage productions, and healthcare. Everyday devices vulnerable to interference include cell phones, FM radios, televisions, and computers.

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Chapter 3: What are the benefits of using electronic enclosures?

The advantages of electronic enclosures vary based on the material used. Manufacturers typically use plastic and metal to fabricate enclosures, which are detailed below.

Benefits of Using Plastic Enclosures

Plastic enclosures offer several benefits, including:

Enclosures are Non-Magnetic

Magnetic interference can affect some electronic devices, but plastic enclosures virtually eliminate this risk as they do not produce magnetic fields.

Enclosures are Insulating

Plastic, like rubber, is an insulator and does not conduct electricity. This makes plastic enclosures ideal for applications where avoiding electrical conductivity is crucial, such as covering motherboards and processors in laptops to prevent short circuits.

Plastic Enclosures are Waterproof

Plastic enclosures are resistant to water and can withstand exposure to humid environments, including water, snow, or rain, without sustaining damage. Unlike metal enclosures, they do not suffer from rust when exposed to moisture.

Cost-Effective Plastic

Plastic is an economical material, making plastic enclosures more affordable compared to metal options. This cost-effectiveness makes them a popular choice for many applications.

Plastic Enclosures are Lightweight

The lightweight nature of plastic enclosures makes them particularly suitable for portable electronic devices. Items such as car remotes, game controllers, cell phones, and chargers benefit from this characteristic.

Flexible Enclosures

Plastic enclosures can be easily shaped into complex forms due to their flexible chemical structure, allowing for precise fittings and custom designs.

Benefits of Using Metal Enclosures

Aluminum and stainless steel are commonly used metals for electronic enclosures. This section outlines their benefits, though these advantages extend beyond just these two metals.

Benefits of Aluminum Electronic Enclosures

• They resist corrosion and rusting.
• They block radio frequencies from passing through them.
• They can resist high temperatures.
• The scrap is easily recyclable.
• Aluminum enclosures can resist UV light.
• They are lightweight when compared to steel.

Benefits of Stainless Steel Electronic Enclosures

• They can withstand harsh and rigorous operating conditions.
• They have longevity and can retain their structure and appearance.
• Using stainless steel enclosures will not affect the color, flavor, and odor of food.
• Good hygiene is easy to maintain when using stainless steel.
• They are durable.
• They are cost-effective and fire-resistant.

Considerations When Choosing an Electronic Enclosure

When selecting an electronic enclosure, several factors should be considered:

Environmental Conditions

Electronic devices are integral to many aspects of daily life and are used across various industries. These devices operate in diverse environments, which can range from harsh to mild. Designing an electronic enclosure requires evaluating the specific environmental conditions it will face, such as exposure to sunlight, dust, rain, vibrations, or chemicals. Understanding these conditions will aid in choosing the appropriate material for the enclosure.

Industry Design Standards and Performance

Compliance with industry standards and regulations is crucial when designing electronic enclosures. Organizations like the International Electrotechnical Commission (IEC) and various government bodies set guidelines and specifications that must be adhered to. These standards define the necessary product specifications, and ensuring conformity is essential for creating a functional and compliant enclosure.

Thermal Requirements

Understanding the thermal dynamics of the electronic components being protected is vital. It's important to know the amount of heat generated by the internal components, such as regulators, resistors, LEDs, and power circuits. While plastics are effective insulators, they may melt under high temperatures, so they are best suited for low-heat applications. Metals, on the other hand, are more suitable for enclosures dealing with high heat dissipation.

Types of Materials in Enclosures

Today, various materials can be used for enclosures, with choices influenced by factors like cost, weight, size, and aesthetics. Acrylic is a popular and cost-effective option due to its lightweight, impact resistance, and flexibility. Polycarbonate is also favored for its thermal stability and impact resistance. Other materials such as aluminum, glass, copper, and steel are used depending on cost considerations and specific application needs.

Electromagnetic Compatibility (EMC)

For a system to be electromagnetically compatible, it must meet specific characteristics that ensure proper operation without interference.

• The system does not cause interference to other systems or equipment surrounding it.
• The system should not be affected by emissions from other systems or equipment such as electromagnetic fields created by other circuits.
• The system should not cause interference within itself.

The diagram below illustrates how emissions are distributed in electrical and electronic devices.

Conclusion

The electronic industry is fast-growing, and this is evident especially when we look at the portable electronic devices that almost the whole world has been exposed to. We use devices like cell phones, radios, microwaves, remote control, laptops, etc on a daily basis and the information provided in this article will give either the consumer or the manufacturer of these devices some insight on how best to interact with these electronic enclosures.

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